(1) Technical Field
This invention relates to a pick and place apparatus for small articles, and more particularly, is concerned with improvements for the adjustment of a pick and place vacuum probe apparatus for high speed handling of semiconductor devices.
(2) Description of the Prior Art
Today's semiconductor devices, such as integrated circuit dice are increasing in production numbers and functionality, while decreasing in size and unit cost. For handling, as example, during test, surface mount, and other operations requiring individual processing. This is done by fully automating the handling of these small devices during the individual process operations while reducing handling downtime.
Generally, testing operations take place upon individual semiconductor chips in a high speed manner. Chips must be contained and presented to the handler in a convenient manner. Therefore, chip containers which carry a multiplicity of chips are queued at the chip handler and readied for high speed, yet, discreet handling in a first in, first out manner.
Chip handlers which are an integral part of most testing apparatus operate in a high speed pick and place manner. Conventionally, a pick and place probe translates to a chip pick-up position, lowers to take hold of the chip, raises the chip from its container, translates to a test socket, as an example, then lowers the chip for test, after test, translates back to the container and places the chip back in its container position. The description given for pick and place is a simplified translation, it may entail additional place positions, as example, placing the good chips back into their original container position, and sorting the defective chips into several defect categorized containers.
The focus of this invention is directed to a high speed SMD pick and place handler, and more particularly, to a modification of a contactor sleeve assembly such as that used on models Synax, SX141 H, and SX141C, IC test handlers, manufactured by Shinano Electronics Company Ltd., Japan.
Each of the aforementioned handlers uses similar contactor sleeve assemblies. Referring now to FIG. 1, the contactor sleeve assembly 21 is mounted and carried by an aluminum body contactor housing 22. The contactor sleeve assembly consists of an outer hollow tube 25 having a device suction cup 28 at its distal end and a threaded hole along its longitudinal axis for engagement of a locking set screw 26. The outer hollow tube is guided by an inner hollow post 27 and is adjustable by manually loosening the locking set screw 26 permitting movement of the outer hollow tube 25 for vertical adjustment of the device suction cup 28 relative to a horizontal reference plane 10. The inner hollow post 27 has a flat area on one side of its circular shape for the tightening of the set screw 26 which applies a force normal to the vertical axis which drives the opposite side of the outer tube in a higher frictional contact with the inner post surface thus holding the outer hollow tube 25 in its vertically adjusted position. A barbed fitting 29 at the proximal end of the hollow inner post 27 communicates a vacuum pressure to the suction cup 28.
The high acceleration speeds of the pick and place handler causes loosening of mechanical settings, particularly, the vertical setting associated with the vacuum suction cup 28 on the contactor sleeve assembly 21 in relation to a chip surface. Although some vertical compliance exists between the vacuum suction cup and device, it can be transitory, therefore, a maintenance schedule is put into place for resetting the contactor sleeve assembly.
Because of the physical arrangement of the contactor head assembly 21 and the present method for locking the sleeve assembly using a set screw 26, adjustment is extremely difficult to accomplish. Both hands are required to do the adjustment. Location of the set screw is not visible from a frontal access, therefore a maintenance person must feel for the set screw position, fit a tool into a keyed recess of the set screw, loosen the set screw while holding and adjusting the body of the sleeve assembly to a fixed reference, then tightening the set screw. Since the stainless steel body of the sleeve assembly is mounted on an aluminum contactor housing 22, a differential in the coefficient of thermal expansion between the two materials causes problems during high/low temperature testing and at times necessitates forcing the adjustment of the sleeve assembly which results in damage to the sleeve assembly.